Rock Characteristics

Phaneritic Texture

igneous rock texture in which minerals are easily visible without magnification (indicates a long time to cool)

Aphanitic Texture

A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished without the aid of a microscope (indicates fast cool time)

Porphyritic Textrue

an igneous texture consisting of large crystals embedded in a matrix of much smaller crystals (typically this rock started cooling underground and was disturbed causing it to finish cooling quickly above ground)

Vesicular Texture

ingeous rock texture that has a lot of holes & bubbles (these rocks are often formed from ash)

Pyroclastic Texture

an igneous rock comprised of a bunch of ash & crystal grains

Glassy Texture

An igenous texture formed when a rock cools so fast it doesn't have time to crystallize, rather it forms a smooth glassy surface (typically found from surfaces of lava flows)

Adamantine Luster

exceptionally bright and reflective (diamond)

Vitreous Luster

shines like glass

Sub-Vitreous Luster

slightly less shiny than glass

Pearly Luster

looks like a pearl, a reserved sort of sheen

Silky Luster

shines like silk, the surface of the mineral is slightly textured

Greasy Luster

surface of the mineral looks covered in grease

Earthy Luster

mineral is naturally very dull, no shine

Amphibole (Hornblende)

a mineral with vitreous luster, is dark green/black in color (mafic), grey/white streak, hardness of 5/6

Biotite (Mica)

a mineral with viterous luster, is dark brown/black in color (mafic), greay streak, hardness of 2.2/3, and has cleavage in 1 perfect direction

Calcite

a mineral with vitreous luster, can be many colors, white streak, hardness of 3, and has 3 perfect planes of cleavage

Feldspar

a mineral with viterous luster, is pink/white/grey in color, white streak, hardness of 6/6.5

Fluorite

a mineral with vitreous luster, is green/blue/purple in color, white streak, hardness of 4, and fractures in uneven flat surfaces while having 4 planes of cleavage

Graphite

a mineral with sub-metalic luster, is grey in color, dark grey streak, hardness of 1.5/2, often used for pencils

Gypsum

a mineral is white or clear in color, white streak, hardness of 2

Halite (Salt)

a mineral with a greasy luster, is clear or white in color, white streak, hardness of 2.5, and has perfect cleavage in 3 directions

Hematite

a mineral with either a metalic or earthy luster, is grey/brown/red in color, maroon streak, hardness of 6.5, has weak magnetism

Magnatite

a mineral with a metalic luster, is grey/black in color, hardness of 5.5/6, cleavage in one direction, is strongly magnetic

Muscovite (Mica)

Vitreous luster, light brown/clear in color (felsic), white streak, hardness of 2.5/3, perfect cleavage in one direction

Olivine

vitreous luster, green color (mafic), white streak, hardness of 6

Pyrite

metalic luster, brass yellow color, green/gray/black streak, hardness of 6.5

Pyroxene

vitreous luster, mafic coloring, green streak, hardness of 5, 2 planes of perfect cleavage

Quartz

vitreous luster, any color, white streak, hardness of 7, conchoidial fracture

Talc

pearly/greasy luster, white color and streak, hardness of 1

Granite

igneous rock with phaneritic texture and felsic composition

Diorite

igneous rock with phaneritic texture and intermediate composition

Gabbro

igneous rock with phaneritic texture and mafic composition

Rhyolite

igneous rock with aphanitic texture and felsic composition

Andesite

igneous rock with aphanitic texture and intermediate composition

Basalt

igneous rock with aphanitic texture and mafic composition

Pumice

igneous rock with a vesicular texture and felsic composition

Scoria

igneous rock with a vesicular texture and mafic composition

Vesicular Basalt

igenous rock with a vesicular texture and mafic composition, however this rock is much heavier than its vesicular rock counterparts

Porphyritic Andesite

igneous rock with porphyritic texture and intermediate composition

Volcanic Tuff

igneous rock with pyroclastic texture & mafic to felsic composition

Obsidian

igneous rock with glassy texture and mafic composition

Clastic Sedimentary Rock

composed of other rock fragments cemented by silicate minerals, grain size dictates what the name of the rock is

Biochemical Sedimentary Rock

composed of organisms and material that dissolved in solution to form a rock, often are very reactive to acid

Organic Sedimentary Rock

composed of dead organisms

Breccia

clastic rock with large, angular, poorly sorted grains

Conglomerate

clastic rock with large, rounded, poorly sorted grains

Sandstone

clastic rock with course, rounded, well sorted sand grains

Shale

clastic rock with fine, rounded, well sorted mud & clay grains

Coquina

biochemical rock composed of shell fragments, reacts with acid

Fossiliferous Limestone

biochemical rock that is poorly sorted, contains fossils, acid reactive

Microcrystaline Limestone

biochemical rock that is well sorted, acid reactive

Chalk

biochemical rock composed of fine shell fragments, acid reactive

Coal

organic rock, there are different stages , the youngest being called peat

Rock Gypsum

very soft chemical rock, is an evaporite

Rock Salt

chemical rock made up of halite, is an evaporite

Chert

chemical rock that is composed of icrocrystaline quartz, is NOT acid reactive

Slate

low grade metamorphic rock, shale protolith

Phyllite

low grade metamorphic rock, satin luster, slate protolith

Schist

medium grade metamorphic rock, glittery shiny luster, phyllite protolith

Gneiss

high grade metamorphic rock, clear foliation and distinct banding of dark and light minerals, schist protolith

Migmatite

high grade metamorphic rock, experiences some partial melting, migmatite protolith

Quartzite

recrystalized quartz crystals, sandstone protolith

Marble

recyrstalized calcite, limestone protolith

Chemical Sedimentary Rock

forms when minerals become supersaturated in a solution and precipitate to form a rock